Speculative execution is a workaround for the fact that CPUs read and process data much more quickly than main memory can provide it. The CPU tries to trace as

Speculative execution is a workaround for the fact that CPUs read and process data much more quickly than main memory can provide it. The CPU tries to trace as many code-paths as possible so it can discover which memory addresses are likely to be used in the near future and queue them up so they'll be ready in the local cache when they're needed. Smarter compilers wouldn't really help, this is all about how the code is running for the next millisecond on this specific workload on this specific CPU, rather than how it's running today or on this cluster or in general.